Internet Magic (Proxy Server) Windows Application

using System;
using System.Net;
using System.Net.Sockets;
using internet_magic;
using internet_magic.Socks.Authentication;

namespace internet_magic.Socks {

///<summary>Relays data between a remote host and a local client, using the SOCKS protocols.</summary>
///<remarks>This class implements the SOCKS4, SOCKS4a and SOCKS5 protocols.</remarks>
///<remarks>If the MustAuthenticate property is set, only SOCKS5 connections are allowed and the AuthList parameter of the constructor should not be null.</remarks>
public sealed class SocksClient : Client {
	///<summary>Initializes a new instance of the SocksClient class.</summary>
	///<param name="ClientSocket">The Socket connection between this proxy server and the local client.</param>
	///<param name="Destroyer">The method to be called when this SocksClient object disconnects from the local client and the remote server.</param>
	///<param name="AuthList">The list with valid username/password combinations.</param>
	///<remarks>If the AuthList is non-null, every client has to authenticate before he can use this proxy server to relay data. If it is null, the clients don't have to authenticate.</remarks>
	public SocksClient(Socket ClientSocket, DestroyDelegate Destroyer, AuthenticationList AuthList) : base(ClientSocket, Destroyer) {
		this.AuthList = AuthList;
	}
	///<summary>Gets or sets the SOCKS handler to be used when communicating with the client.</summary>
	///<value>The SocksHandler to be used when communicating with the client.</value>
	internal SocksHandler Handler {
		get {
			return m_Handler;
		}
		set {
			if (value == null)
				throw new ArgumentNullException();
			m_Handler = value;
		}
	}
	///<summary>Gets or sets the SOCKS handler to be used when communicating with the client.</summary>
	///<value>The SocksHandler to be used when communicating with the client.</value>
	public bool MustAuthenticate {
		get {
			return m_MustAuthenticate;
		}
		set {
			m_MustAuthenticate = value;
		}
	}
	///<summary>Starts communication with the client.</summary>
	public override void StartHandshake() {
		try {
            
			ClientSocket.BeginReceive(Buffer, 0, 1, SocketFlags.None, new AsyncCallback(this.OnStartSocksProtocol), ClientSocket);
		} catch {
			Dispose();
		}
	}
	///<summary>Called when we have received some data from the client.</summary>
	///<param name="ar">The result of the asynchronous operation.</param>
	private void OnStartSocksProtocol(IAsyncResult ar) {
		int Ret;
		try {
            
			Ret = ClientSocket.EndReceive(ar);
			if (Ret <= 0) {
				Dispose();
				return;
			}
			if (Buffer[0] == 4) { //SOCKS4 Protocol
				if (MustAuthenticate) {
					Dispose();
					return;
				} else {
					Handler = new Socks4Handler(ClientSocket, new NegotiationCompleteDelegate(this.OnEndSocksProtocol));
				}
			} else if(Buffer[0] == 5) { //SOCKS5 Protocol
				if (MustAuthenticate && AuthList == null) {
					Dispose();
					return;
				}
				Handler = new Socks5Handler(ClientSocket, new NegotiationCompleteDelegate(this.OnEndSocksProtocol), AuthList);
			} else {
				Dispose();
				return;
			}
			Handler.StartNegotiating();
		} catch {
			Dispose();
		}
	}
	///<summary>Called when the SOCKS protocol has ended. We can no start relaying data, if the SOCKS authentication was successful.</summary>
	///<param name="Success">Specifies whether the SOCKS negotiation was successful or not.</param>
	///<param name="Remote">The connection with the remote server.</param>
	private void OnEndSocksProtocol(bool Success, Socket Remote) {
		DestinationSocket = Remote;
		if (Success)
			StartRelay();
		else
			Dispose();
	}
	///<summary>Gets or sets the AuthenticationList to use when a computer tries to authenticate on the proxy server.</summary>
	///<value>An instance of the AuthenticationList class that contains all the valid username/password combinations.</value>
	private AuthenticationList AuthList {
		get {
			return m_AuthList;
		}
		set {
			m_AuthList = value;
		}
	}
	///<summary>Returns text information about this SocksClient object.</summary>
	///<returns>A string representing this SocksClient object.</returns>
	public override string ToString() {
		try {
			if (Handler != null)
				return Handler.Username + " (" + ((IPEndPoint)ClientSocket.LocalEndPoint).Address.ToString() +") connected to " + DestinationSocket.RemoteEndPoint.ToString();
			else
				return "SOCKS connection from " + ((IPEndPoint)ClientSocket.LocalEndPoint).Address.ToString();
		} catch {
			return "Incoming SOCKS connection";
		}
	}
	// private variables
	/// <summary>Holds the value of the AuthList property.</summary>
	private AuthenticationList m_AuthList;
	/// <summary>Holds the value of the MustAuthenticate property.</summary>
	private bool m_MustAuthenticate = false;
	/// <summary>Holds the value of the Handler property.</summary>
	private SocksHandler m_Handler;
}

}